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How to solve the boundary layer without wall functions? |
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March 17, 2016, 08:31 |
How to solve the boundary layer without wall functions?
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#1 |
Member
Join Date: Dec 2015
Posts: 74
Rep Power: 11 |
Dear Foamers,
I'm using OpenFOAM 2.3.0. What conditions have I to set on k and omega parameters if I want to solve the boundary layer with k-omega SST model? I have a mesh with a y+ less than 4 in the wall patches; however, I think the conditions with wall functions are not correct: omega: Code:
"(wall_1|wall_2)" { type omegaWallFunction; value $internalField; } k Code:
"(wall_1|wall_2)" { type kqRWallFunction; value $internalField; } } I tried to use: omega: Code:
"(wall_1|wall_2)" { type zeroGradient; } k Code:
"(wall_1|wall_2)" { type zeroGradient; } } Code:
Selecting RAS turbulence model kOmegaSST --> Upgrading k to employ run-time selectable wall functions Backup original k to k.old Writing updated k --> Upgrading omega to employ run-time selectable wall functions Backup original omega to omega.old Writing updated omega --> Creating mut to employ run-time selectable wall functions Writing new mut --> Creating alphat to employ run-time selectable wall functions Writing new alphat Witch is the correct setting? Thanks, WhiteW |
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March 20, 2016, 06:31 |
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#2 |
Member
Join Date: Dec 2015
Posts: 74
Rep Power: 11 |
Any idea?
WhiteW |
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March 21, 2016, 04:34 |
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#3 |
Senior Member
Alex
Join Date: Jan 2014
Posts: 126
Rep Power: 12 |
Well you would not set k and omega to zeroGradient, but to a very small, non zero fixedValue. For example:
k: fixedValue, value uniform 1e-8 However, the omega wall function is known to work well with lowRe meshes as it only applies the correct omega value to the wall without much of damping or blending. So i'd suggest just switching k to a fixedValue. |
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March 21, 2016, 06:41 |
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#4 |
Member
Join Date: Dec 2015
Posts: 74
Rep Power: 11 |
Thanks for the reply. Now I left omega with the wallFunction and I set k as:
Code:
"(wall_1|wall_2)" { type fixedValue; value uniform 1e-8; } Code:
Selecting RAS turbulence model kOmegaSST --> Upgrading k to employ run-time selectable wall functions Backup original k to k.old Writing updated k --> Upgrading omega to employ run-time selectable wall functions Backup original omega to omega.old Writing updated omega --> Creating mut to employ run-time selectable wall functions Writing new mut --> Creating alphat to employ run-time selectable wall functions Writing new alphat Code:
"(wall_1|wall_2)" { type compressible::kqRWallFunction; value uniform 1e-08; } |
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January 20, 2020, 05:55 |
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#5 | |
New Member
Hans
Join Date: Oct 2019
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Quote:
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